Effects of oxygen on exercise-induced increase of pulmonary arterial pressure in idiopathic pulmonary fibrosis.

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a severe disease with no known effective therapy. Patients with IPF may develop severe increase of pulmonary arterial pressure (PAP) on exercise, the mechanisms of which is not clearly identified.

OBJECTIVES

To determine whether oxygen may correct the increase of PAP developed during exercise in patients with IPF.

PATIENTS AND METHODS

We performed a prospective study on patients with IPF and no hypoxaemia at rest. The absence of pulmonary hypertension (PH) at rest was confirmed by echocardiography (systolic PAP <35 mmHg). Eight patients underwent echocardiography during exercise in air and with oxygen (to maintain saturation of at least 94%). Right ventricle-right atrium gradient and cardiac output were measured at rest, after each increment and at peak. We then compared the echocardiographic results obtained for air and oxygen.

RESULTS

All patients developed significant increase of SPAP on exercise (73 +/- 14 mmHg in air). Oxygen did not significantly improve SPAP on exercise (SPAP: 76 +/- 15 mmHg). Echocardiographic characteristics were similar between air and oxygen except for exercise tolerance in term of workload (p=0.045) and endurance (p=0.017). Resting pulmonary function tests did not predict the occurrence of increase of PAP on exercise.

CONCLUSION

Our results demonstrate that oxygen does not improve exercise-induced increase of PAP in patients with IPF and support the hypothesis that hypoxic vaso-constriction is not the main mechanism of acute increase of PAP during exercise.